Kth Largest Element in an Array

题目：

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.

For example,

Given

[3,2,1,5,6,4]

and k = 2, return 5.

Note:

You may assume k is always valid, 1 ≤ k ≤ array's length.
解题思路1：
第一反应就是先排序，再求出对应的数。

后来看到tags是，以后再改！！！！

class Solution(object):

def findKthLargest(self, nums, k):

"""

:type nums: List[int]

:type k: int

:rtype: int

"""

nums.sort()

length = len(nums)

return nums[length-k]

思路2：

可以利用快排的思路解题

class Solution {
public:
int findKthLargest(vector<int>& nums, int k) {
int index = rand()%nums.size(), cur = nums[index];
vector<int> big, small;

for(int i=0;i<nums.size();i++)
{
if(i==index)continue;
if(nums[i]>=cur)
big.push_back(nums[i]);
else
small.push_back(nums[i]);
}

if(big.size()==k-1)
return cur;
else if(big.size()>k-1)
return findKthLargest(big,k);
else
return findKthLargest(small,k-1-big.size());

}
};